Just bought my 1st Jeep about a month ago, it has 85,000 miles with a 5.7 L engine. I took a look at my spark plugs that look they have never been replaced. Is now a good time to change them or is it the 100,000 mark? If so, do I replace the spark plug wire as well?

Most new engines use a coil pack, so no to your question. Just the plug, the coil packs cost alot to replace so be VERY careful with them, but there is no reason to replace one unless its bad. When you go in there to do this job your gonna be surprised if your looking for plug wires, you will see a semi square box with a bolt on it, take the bolt out and gently but firmly wiggle/pull up on the box and the pack will come up, then you drop the socket down there and take out the plug. Oh and btw, if you have the 5.7 hemi you need 16 plugs, not just 8.

Welcome to the forum. With 85K on an 05 Hemi, you may want to at least check the resistance of the ignition wires. Some have had bad wires with less mileage than you have. Rule of thumb used to be no more than 10000 ohms per foot of wiring, but normally should be a lot less than that. I just went and checked my old original wires (less than 20K on them) and one ~3 ft. wire had a total resistance of ~12K ohms. Anyway, if any exceed or are close to being bad, replace the whole set. At that point, you may want to consider switching to the Taylor Shorty wires. I've had them on my 05 Hemi LX for over 5 years now, without issue. It also cleans up that "rat's nest" over the top of the intake manifold.

Over in the LX community the Taylor Shorty wires were a big discussion item when they first came out. By putting them on it eliminates the "wasted spark" system that Chrysler used in 05 only. Obviously it didn't work as desired. Dyno testing showed a loss of ~1-3 hp with the Shorties. You couldn't prove it by me though, but then who can feel 1-3 hp. in the seat of the pants.

Since this vehicle is new to you, I would recommend you go through everything in the drivetrain (engine, transmission, transfer case, differentials) to verify status and condition. There were some issues and TSB's, especially on the early ones. It'll save you $$$ down the road. You may want to also consider cleaning the back side of the throttle body and then install a catch can to prevent it from ever looking like it does before you clean it. You may even see oil puddling in the intake plenum area. Change the PCV Valve also. Install with the valve exit hole facing aft. That will prevent the bypassed oil from having a direct shot to the intake manifold. One other fairly common issue with the Hemi's is the EGR Valve. Many, including me, have had failures in the 40-60K mileage range. Mine went out at about 54K. Common symptoms are reduced performance/economy, low speed surging, and sometimes erratic, almost stalling idle. When you change the spark plugs, use only copper core....not platinums. Some have had misfire issues, especially with the early Hemi's, when using platinum plugs. I use NGK LZTR4A-11, Stock No. 5306 in both my Hemi's, and they have worked great.

Hope this gets you going in the right direction. I am sure others can add more too.

Welcome to the forum. With 85K on an 05 Hemi, you may want to at least check the resistance of the ignition wires. Some have had bad wires with less mileage than you have. Rule of thumb used to be no more than 10000 ohms per foot of wiring, but normally should be a lot less than that. I just went and checked my old original wires (less than 20K on them) and one ~3 ft. wire had a total resistance of ~12K ohms. Anyway, if any exceed or are close to being bad, replace the whole set. At that point, you may want to consider switching to the Taylor Shorty wires. I've had them on my 05 Hemi LX for over 5 years now, without issue. It also cleans up that "rat's nest" over the top of the intake manifold.

Over in the LX community the Taylor Shorty wires were a big discussion item when they first came out. By putting them on it eliminates the "wasted spark" system that Chrysler used in 05 only. Obviously it didn't work as desired. Dyno testing showed a loss of ~1-3 hp with the Shorties. You couldn't prove it by me though, but then who can feel 1-3 hp. in the seat of the pants.

Since this vehicle is new to you, I would recommend you go through everything in the drivetrain (engine, transmission, transfer case, differentials) to verify status and condition. There were some issues and TSB's, especially on the early ones. It'll save you $$$ down the road. You may want to also consider cleaning the back side of the throttle body and then install a catch can to prevent it from ever looking like it does before you clean it. You may even see oil puddling in the intake plenum area. Change the PCV Valve also. Install with the valve exit hole facing aft. That will prevent the bypassed oil from having a direct shot to the intake manifold. One other fairly common issue with the Hemi's is the EGR Valve. Many, including me, have had failures in the 40-60K mileage range. Mine went out at about 54K. Common symptoms are reduced performance/economy, low speed surging, and sometimes erratic, almost stalling idle. When you change the spark plugs, use only copper core....not platinums. Some have had misfire issues, especially with the early Hemi's, when using platinum plugs. I use NGK LZTR4A-11, Stock No. 5306 in both my Hemi's, and they have worked great.

Hope this gets you going in the right direction. I am sure others can add more too.

Thanks for the rep, viking. One other thing came to mind after writing the above post. I now have 65850 on my 06 WK. I have recently replaced the O2 Sensors too. If a newly purchased, used vehicle has been gone through as indicated above, and the fuel economy still sucks, I would recommend changing them. After I did mine, I did a thread on O2 Sensors to hopefully enlighten other forum members on some of the stuff I discovered in my research. Here's the ref. to the thread: http://jeepgarage.org/showthread.php?t=20300